Releases v1.0.0 to support RP2040-based boards
### Initial Releases v1.0.0 1. Initial coding to support RP2040-based boards such as RASPBERRY_PI_PICO. etc. using [Earle Philhower's arduino-pico core](https://github.com/earlephilhower/arduino-pico)
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Khoi Hoang
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/****************************************************************************************************************************
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RPM_Measure.ino
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RPi_Pico_ISR_Timer-Impl.h
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For RP2040-based boards such as RASPBERRY_PI_PICO, ADAFRUIT_FEATHER_RP2040 and GENERIC_RP2040.
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Written by Khoi Hoang
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Built by Khoi Hoang https://github.com/khoih-prog/RPI_PICO_TimerInterrupt
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Licensed under MIT license
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The RPI_PICO system timer peripheral provides a global microsecond timebase for the system, and generates
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interrupts based on this timebase. It supports the following features:
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• A single 64-bit counter, incrementing once per microsecond
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• This counter can be read from a pair of latching registers, for race-free reads over a 32-bit bus.
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• Four alarms: match on the lower 32 bits of counter, IRQ on match: TIMER_IRQ_0-TIMER_IRQ_3
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Now even you use all these new 16 ISR-based timers,with their maximum interval practically unlimited (limited only by
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unsigned long miliseconds), you just consume only one RPI_PICO timer and avoid conflicting with other cores' tasks.
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The accuracy is nearly perfect compared to software timers. The most important feature is they're ISR-based timers
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Therefore, their executions are not blocked by bad-behaving functions / tasks.
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This important feature is absolutely necessary for mission-critical tasks.
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Based on SimpleTimer - A timer library for Arduino.
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Author: mromani@ottotecnica.com
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Copyright (c) 2010 OTTOTECNICA Italy
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Based on BlynkTimer.h
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Author: Volodymyr Shymanskyy
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Version: 1.0.0
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Version Modified By Date Comments
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------- ----------- ---------- -----------
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1.0.0 K Hoang 11/05/2021 Initial coding to support RP2040-based boards such as RASPBERRY_PI_PICO. etc.
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*****************************************************************************************************************************/
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/*
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Notes:
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Special design is necessary to share data between interrupt code and the rest of your program.
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Variables usually need to be "volatile" types. Volatile tells the compiler to avoid optimizations that assume
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variable can not spontaneously change. Because your function may change variables while your program is using them,
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the compiler needs this hint. But volatile alone is often not enough.
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When accessing shared variables, usually interrupts must be disabled. Even with volatile,
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if the interrupt changes a multi-byte variable between a sequence of instructions, it can be read incorrectly.
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If your data is multiple variables, such as an array and a count, usually interrupts need to be disabled
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or the entire sequence of your code which accesses the data.
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RPM Measuring uses high frequency hardware timer 1Hz == 1ms) to measure the time from of one rotation, in ms
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then convert to RPM. One rotation is detected by reading the state of a magnetic REED SW or IR LED Sensor
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Asssuming LOW is active.
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For example: Max speed is 600RPM => 10 RPS => minimum 100ms a rotation. We'll use 80ms for debouncing
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If the time between active state is less than 8ms => consider noise.
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RPM = 60000 / (rotation time in ms)
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You can also use interrupt to detect whenever the SW is active, set a flag then use timer to count the time between active state
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*/
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#if !( defined(ARDUINO_RASPBERRY_PI_PICO) || defined(ARDUINO_ADAFRUIT_FEATHER_RP2040) || defined(ARDUINO_GENERIC_RP2040) )
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#error This code is intended to run on the RASPBERRY_PI_PICO platform! Please check your Tools->Board setting.
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#endif
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// These define's must be placed at the beginning before #include "TimerInterrupt_Generic.h"
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// _TIMERINTERRUPT_LOGLEVEL_ from 0 to 4
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// Don't define _TIMERINTERRUPT_LOGLEVEL_ > 0. Only for special ISR debugging only. Can hang the system.
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#define TIMER_INTERRUPT_DEBUG 1
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#define _TIMERINTERRUPT_LOGLEVEL_ 4
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#include "RPi_Pico_TimerInterrupt.h"
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#define PIN_D1 1 // Pin D1 mapped to pin GPIO1 of RPI_PICO
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unsigned int SWPin = PIN_D1;
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#define TIMER0_INTERVAL_MS 1
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#define DEBOUNCING_INTERVAL_MS 80
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#define LOCAL_DEBUG 1
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// Init RPI_PICO_Timer, can use any from 0-15 pseudo-hardware timers
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RPI_PICO_Timer ITimer0(0);
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volatile unsigned long rotationTime = 0;
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float RPM = 0.00;
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float avgRPM = 0.00;
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volatile int debounceCounter;
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bool TimerHandler0(struct repeating_timer *t)
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{
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if ( !digitalRead(SWPin) && (debounceCounter >= DEBOUNCING_INTERVAL_MS / TIMER0_INTERVAL_MS ) )
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{
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//min time between pulses has passed
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RPM = (float) ( 60000.0f / ( rotationTime * TIMER0_INTERVAL_MS ) );
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avgRPM = ( 2 * avgRPM + RPM) / 3,
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#if (TIMER_INTERRUPT_DEBUG > 0)
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Serial.print("RPM = "); Serial.print(avgRPM);
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Serial.print(", rotationTime ms = "); Serial.println(rotationTime * TIMER0_INTERVAL_MS);
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#endif
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rotationTime = 0;
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debounceCounter = 0;
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}
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else
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{
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debounceCounter++;
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}
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if (rotationTime >= 5000)
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{
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// If idle, set RPM to 0, don't increase rotationTime
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RPM = 0;
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#if (TIMER_INTERRUPT_DEBUG > 0)
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Serial.print("RPM = "); Serial.print(RPM); Serial.print(", rotationTime = "); Serial.println(rotationTime);
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#endif
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rotationTime = 0;
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}
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else
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{
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rotationTime++;
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}
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return true;
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}
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void setup()
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{
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pinMode(SWPin, INPUT_PULLUP);
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Serial.begin(115200);
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while (!Serial);
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delay(100);
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Serial.print(F("\nStarting RPM_Measure on ")); Serial.println(BOARD_NAME);
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Serial.println(RPI_PICO_TIMER_INTERRUPT_VERSION);
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Serial.print(F("CPU Frequency = ")); Serial.print(F_CPU / 1000000); Serial.println(F(" MHz"));
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// Using ESP32 => 80 / 160 / 240MHz CPU clock ,
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// For 64-bit timer counter
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// For 16-bit timer prescaler up to 1024
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// Interval in microsecs
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if (ITimer0.attachInterruptInterval(TIMER0_INTERVAL_MS * 1000, TimerHandler0))
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{
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Serial.print(F("Starting ITimer0 OK, millis() = ")); Serial.println(millis());
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}
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else
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Serial.println(F("Can't set ITimer0. Select another freq. or timer"));
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Serial.flush();
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}
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void loop()
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{
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}
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